Use of gold films as conductors in integrated and thin film circuitry is widespread in the electronics industry. In order to form intricate circuitry patterns, these gold films must be able to be accurately and rapidly etched away with no adverse effect on nearby areas. In the past, standard practice has been to etch gold films with hot aqua regia, basic ferricyanide solutions, or potassium iodide-iodine solutions. Use of such etchant solutions has not been entirely satisfactory, however, due to problems in handling such solutions.
For example, aqua regia is a very strong acid which requires careful handling. Likewise, MacArthur et al., U.S. Pat. No. 3,816,317, which uses a strongly basic ferricyanide solution, warn of precautions which must be taken to avoid emission of toxic cyanide gas during the etching process. Iodine solutions are opaque and require periodic rinsing to determine the etching progress.
Accordingly, the need exists in the art for a rapid and yet relatively safe and easy to handle etchant for gold films.